Anti-wear agents are blended with lubricating agents in order to regulate the anti-wear properties to a suitable level. These anti-wear agents are being used in lubricating compositions such as lubricating oils for automotive vehicles, primarily including high-performance engine oils and gear oils, and industrial lubricating oils such as hydraulic oils. Many types of compounds have been proposed for these anti-wear agents.
The most representative of these anti-wear agents are zinc dithiophosphates (referred to as “ZnDTPs” hereinafter). These organozinc compounds are compounds denoted by the following General Formula (1), as can be seen in U.S. Pat. Nos. 2,364,283 and 2,364,284.

Anti-wear properties are important in the performance of lubricating oils, and many techniques for blending various anti-wear agents have been disclosed in the prior art in order to maintain that performance. In particular, the aforementioned ZnDTPs have been used as anti-wear agents for a long time. “Shinpan Sekiyu Seihin Tenkazai” (Petroleum Product Additives, New Edition), edited by Sakurai Toshio and published by Saiwai Shobo Ltd. on 25 Jul. 1986 and the following Patent References also disclose the use of phosphorus-containing compounds having anti-wear properties:
Japanese Patent No. 3662228,
Japanese Patent No. 4166872,
Japanese Laid-open Patent 2001-354987,
Japanese Laid-open Patent 2002-20779, and
Japanese Laid-open Patent 2008-266367.
As mentioned above, anti-wear properties are important in the performance of lubricating oils, and anti-wear agents are being used in lubricating compositions such as high-performance lubricating oils for automotive vehicles and industrial lubricating oils. The techniques of the prior art relating to anti-wear agents used in prior high-performance lubricating oils have nearly all been achieved by the addition of ZnDTPs. In this invention, as the result of intensive research on novel compounds having anti-wear properties, it has been discovered that certain phosphorus compounds having a specified structure have superior anti-wear properties. In other words, the inventors have discovered phosphorus compounds exhibiting superior anti-wear properties of the same order as the ZnDTPs of the prior art, and so have arrived at completion of this invention.